The invention is based on a camshaft for an injection pump as revealed hereinafter. It is known (Austrian Pat. No. 253 300, Austrian Pat. No. 264 209) to support camshafts for injection pumps for internal combustion engines at their ends or, in the case of longer camshafts, as for instance in engines with more than four cylinders, to provide intermediate bearings. However, in the known injection pumps these intermediate bearings are mainly used to avoid possible knocking or uneven running caused by too large an axial play of the camshaft during uneven heat expansion of the injection pump housing on the one hand and the camshaft on the other. In order to offset the differing heat expansion coefficients between injection pump housing and camshaft resulting therefrom, in known injection pumps at least one bearing of the camshaft is fixed and the other axially displacably mounted in the pump housing and the bearings are interconnected with each other by connecting members disposed in the same chamber as the camshaft. Furthermore, the material of the connecting members has substantially the same or almost the same heat expansion coefficient as the material of the camshaft. The construction of the camshaft is such that the shaft has a constant diameter, with the exception of the end bearings, on which the cam means, having the usual noncircular shape, are disposed at the prescribed distance which makes possible the actuation of the pump pushrods.
It is further known in a camshaft for internal combustion engines with fuel injection (German Offenlegungsschrift No. 29 45 873) corresponding to U.S. Pat. No. 4,335,686), to dispose between the cams for the actuation of the usual pushrods of the inlet and outlet valves for the operation of a tappet of a fuel injection pump fuel unit injector. Additionally, it is possible to dispose such pump camming means on the engine camshaft because thepump cam, although overlapping at least one of the adjacent valve pushrods, has a shape in the area of this overlap which lines within a predetermined curve, so that collision between the pump cam and the valve pushrod is impossible.
The known injection pumps cannot correct for sagging or other general problems, such as excessive vibration, in the case of long injection pump camshafts, and insufficient cross-directional rigidity of the camshaft. Such sagging, for example, can create considerable stress at the main bearings and thus can cause irregularities in operation of the mechanism. U.S. Pat. No. 3,272,189 addresses this problem and offers a solution which accepts this conventional type of sagging.